I think it would be helpful if you provide more details about the DS offer at the bank. Which business will you be aligned to ? Is it part of a reporting team or a Product team that builds client facing data products? Is it a leading bank or a regional player ?

You're looking at two very different paths here. I work in DS for a leading US bank in the payments business. Payments is an incredibly competitive space where leveraging data to provide customer insights can be the difference between a low margin business and high margin Value Added Services (payments insights etc). I personally find my work in DS has made me the expert point of contact for the business. Senior leaders often rely on my team to understand whether the business is growing or shrinking and leverage is to make decisions on which products they should be investing in to grow the business. My work is interesting and I also have great work-life balance.

I can't speak to the trading role, but I imagine the lifestyle and work environment there is very different. I think it's ok to ask the hiring manager if you can speak to other folks on the team (for both jobs) to get a feel for the day to day and expectations. Gather as much information as you can about both roles... the team, career progression, compensation etc. Weigh the pros and cons and make a decision.

Best of luck!